Rotary piston combustion engine with oil-cooled piston

ABSTRACT

A rotary piston combustion engine is provided with two separate oil circulating systems. One supplies cooling oil through the piston, while the other serves to lubricate the shaft and piston bearings. Each system has its own oil feed pump with the pump of the lubricating system having a small delivery volume at high pressure, and the pump for the cooling oil system having a large delivery volume at low temperature.

United States Patent 1191 Froede et al. 5] Apr. 8, 1975 1 ROTARY PISTON COMBUSTION ENGINE 3,042,009 7/1962 Froede et al 418/94 WITH OIDCOOLED PISTON 3,131,679 5/1964 Peras 3,261,542 7/1966 Jones [75] Inventors: Walter Froede; Wulf Leitermann, 3330.312 10 19 peras U both of Neckarsulm, Germany 3,359,952 12/1967 Jones et a1... 1 Assignees: Audi NSU Auto Union 3,712,766 l/l973 Jones 418/84 Aktiengesellschaft, Neck rsul FOREIGN PATENTS OlR APPLICATIONS Wurttemberg; Wankel H, 1,916,098 3/1969 Germany 418/84 Lindau/Bodensee, both of, Germany 22] Filed: May 9 1972 Primary E.\'aminer-William L. FI'CCh Attorney, Agent, or FirmKa11e, Dalsimer, Kane, I PP 5 ,703 Sullivan and Kurucz 130 Foreign Application Priority Data ABSTRACT May 10. 1971 Germany 2123011 A rotary piston combustion engine is provided with two separate oil circulating systems. One supplies [52] U.S. Cl. 418/84; 418/87; 418/88 cooling oil through the piston, while the other serves [51 Int. Cl F0lc 21/04; F04c 29/02 to lubricate the shaft and piston bearings. Each system [58] Field of Search 418/84, 87, 88, 94 ha i s own oil feed pump with the pump of the lubricating system having a small delivery volume at high [56] References Cited pressure, and the pump for the cooling oil system hav- UNITED STATES PATENTS ing a large delivery volume at low temperature. 2,936,949 5/1960 Broom 418/88 1 Claim, 1 Drawing Figure 36 17 26 13 22 39 2 l 21 18/ E y 2 \6 t W o l .-2 a.

( \h 27 K, I/ 19 2-1 \J PATENTEDAPR 81975 W 4 WV/ ROTARY PISTON COMBUSTION ENGINE WITH OIL-COOLED PISTON BACKGROUND OF THE INVENTION The invention concerns a rotary piston combustion engine with an oil-cooled piston which is pivoted on the eccentric of an eccentric shaft mounted in the housing of the combustion engine.

In rotary piston combustion engines of this type, the oil used both for lubricating the shaft and piston bearings and for cooling the piston is supplied through a hole in the eccentric shaft from where channels lead to the individual bearings. The cooling of the piston takes place thereby by means of leak oil coming from the piston bearing and forced into the hollow spaces of the piston and/or by means of spray nozzles which are supplied from the hole in the eccentric shaft and spray the cooling oil directly into the hollow spaces of the piston. Upon flowing through the hollow spaces of the piston, the cooling and the leak oil is collected in receivers and then fed into a tank from where it is drawn off by means ofa feed pump. Upon flowing through an oil cooler and an oil filter this oil is again fed into the hole in the eccentric shaft. It may happen that in the case of this type of lubrication and piston cooling the pressure at low speeds will be too low for ensuring a sufficient lubrication of shaft and piston bearings, since the spray nozzles due to their open cross-section prevent the buildup of the required high pressure.

SUMMARY OF THE INVENTION- The object of this invention is to eliminate this disadvantage. For this purpose. the invention proposes that separate oil circulating systems be provided for the cooling oil flowing through the piston and for the oil serving to lubricate the shaft and piston bearings. As a result, the amount of oil and the oil pressure in each oil circulating system may be optimized in accordance with the given requirements.

The present invention makes it possible to adjust the amount of cooling oil flowing through the piston according to the given load of the engine. It has been found that fuel consumption is relatively high at low loads and low speeds. This can be explained by the fact that the working chambers of rotary piston combustion engines as compared to reciprocating engines have a relatively large heat-emitting surface and thus do not reach their operating temperature within the abovementioned working range. In providing a separate oil circulating system for the oil flowing through the piston, the optimal piston temperature at any operating condition can be achieved by providing in the pipe to the piston a valve which is controlled depending on the temperature of the cooling oil in the return pipe and which shuts 'off the feed pipe should the temperature fall below a certain value. Accordingly, the cooling of the piston will be reduced and a higher piston temperature obtained. This will have a favorable effect on the fuel consumption, since especially in the case of rotary piston combustion engines of the trochoidal design. the carburated gas is prepared for combustion on reaching the piston when the latter is hot. In principle, the described valve in the cooling oil supply pipe could be also controlled by speed or load. Thus, the temperature of the cooling oil as it flows out of the piston is a more simple and a more reliable indication ofthe piston temperature.

In arranging separate oil circulating systems for the cooling oil and the lubricating oil, it becomes possible to provide a separate feed pump for each of the two systems. Hitherto the oil for piston cooling and for lubrication was fed by one single pump which had to have a relatively high delivery volume and a high feed pressure, since bearing lubrication requires a relatively high pressure, while on the other hand, piston cooling requires a relatively large delivery volume. An oil pump which meets both requirements must therefore show a relatively high power consumption. In arranging separate oil pumps for each of the oil circulating systems it becomes possible to use for piston cooling, a pump with large delivery volume at low pressure, while for bearing lubrication a pump is used which at a small delivery volume has a high pressure. These two pumps together consume considerably less power than the previous single pump which had to have a large feed volume at high pressure.

BRIEF DESCRIPTION OF THE DRAWING A form of construction in accordance with the present invention shall be described in the following with particular reference to the drawing which shows a longitudinal section of a rotary piston combustion engine.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT The rotary piston combustion engine has a housing which consists of a casing l with a double-bent inner surface 2 and side parts 3 and 4 which are parallel to each other. An eccentric shaft 7 is pivoted on friction bearings 5 and 6 in the side parts 3 and 4. A triangular piston 10 is pivoted by way of a piston bearing 9 on the eccentric 8 of the eccentric shaft 7. The speed of the piston 10 is at a fixed ratio to the speed of the eccentric shaft 7 by way of a transmission consisting of a hollow wheel 11 attached to the piston 10 and a pinion l2 fastened to the side part 3. The piston 10 is provided with hollow spaces 13 through which the coolant flows. In order to prevent the coolant from overflowing into the working chambers 14, a sealing ring 15 is provided on the right side of the eccentric 8; this ring works together with the adjacent front wall of the piston 10. A disc 16 is screwed to the left side of the eccentric 8. This disc 16 carries a sealing ring 17 which works together with the adjacent piston wall as well as a sealing ring 18 which works together with the housing side part 3.

Separate circulating systems are provided for the lubrication of the shaft bearings 5 and 6 and the piston bearing 9 on the one hand, and for the cooling of the piston 10 on the other. The lubrication system has a pump 19 which draws off the lubricating oil from the tank 20 and supplies it by way of channels 21 and 22 in the side parts 3 and 4 to the shaft bearings 5 and 6. The shaft bearing 5 has holes 23 which are connected to one side to the channel 21 and on the other to a cross hole 24 in the eccentric shaft 7.. The cross hole 24 runs into a longitudinal hole 25 in the eccentric shaft 7 from where another cross hole 26 leads to the piston bearing 9. In this way, the piston bearing 9 is supplied with lubricant.

The cooling oil circulating system for the piston 10 has its own pump 27 which likewise draws off oil from the tank 20 and feeds cooling oil by way of a pipe 28 to a cross hole 29 in the eccentric shaft 7. The cross hole 29 runs into the longitudinal hole 25. A pipe 30 is inserted into the said hole 25. This pipe 30 ends before the end of the longitudinal hole 25 and is sealed at 31 and 32 against the wall ofthe hole 25. This space 33 between the end of the pipe 30 and the end of the hole 25 is connected to the hollow spaces 13 of the piston by way of a cross hole 34. The cooling oil is fed by the pump 27 into the hollow spaces 13 of the piston by way of the pipe 28, the cross hole 29, the pipe 30, the space 33 and the cross hole 34. The removal of the cooling oil takes place by way of the ring-shaped space 35 between the hollow wheel 11 and the disc 16 as well as by way of the channel 36 in the side part 3 and the return pipe 37 which leads back to the tank 20. The leak oil coming out of the bearings and 9 is likewise returned to the tank by way of the channel 36 and the pipe 37, while the leak oil from the bearing 6 runs directly back to the tank 20 by way of a channel (not shown in the drawing) in the side part 4.

A valve 38 is provided in the feed channel 28 for the cooling oil. The control piston 39 of the valve is springloaded by means of the spring 40 which tends to hold the piston 39 in a position which partially shuts off the feed pipe 28, as shown in the drawing. The valve 38 is controlled by a temperature responsive device 41 which responds to the temperature of the cooling oil as it flows through the return pipe 37.

When the engine is cold, the control piston 39 will be in the position as shown in which only a partially throttled supply of cooling oil will reach the hollow spaces 13 of the piston. When the engine reaches its operating temperature which will be indicated by a corresponding temperature of the cooling oil flowing through the return pipe 37, the valve piston 39 will be shifted to the left in the drawing by the temperature responsive device 41 with the result that the annular tee-slot 42 in the valve piston 39 will be in the plane of the feed pipe 28 so that a larger cooling oil amount will be supplied to the piston 10. Thus, by means of the valve 38, the

piston 10 will quickly reach its operating temperature.

Instead of a valve 38 responding to the temperature of the cooling oil in the return pipe 37 another valve responding to speed and/or load could be provided which would throttle the feed pipe 28 at low loads and low speeds.

In arranging two separate oil circulating systems, one for the cooling oil and another for the lubricant, it not only becomes possible to throttle the cooling oil supply until operating temperature has been reached, but it also offers the advantage that a sufficiently high lubricating oil pressure will be already available at low speeds. A further advantage is that in line with the requirements, the pump 19 for bearing lubrication can be designed for a small delivery volume at high pressure and the pump 27 for the cooling oil for a large delivery volume at low pressure. In a finished engine, the ratio of delivery volumes of the pumps 19 and 27 is approximately 1:4, whereby the lubricating oil pump 19 delivers with a pressure of approximately 5 atmospheres gage pressure and the cooling oil pump with a pressure of approximately 3 atmospheres gage pressure. Both pumps together consume less power than the hitherto commonly used single pump for both lubricating and cooling oil which had to be designed for a large delivery volume at high pressure.

Thus, the several aforenoted objects and advantages are most effectively attained. Although several preferred embodiments have been shown and described in detail herein, it should be understood that this invention is in no sense limited thereby and its scope is to be determined by the appended claims.

What is claimed is:

l. A rotary piston combustion engine comprising:

a housing, a shaft mounted in the housing, shaft bearings interposed between the shaft and the housing, an eccentric on the shaft, a rotary piston carried by the eccentric, a piston bearing interposed between the eccentric and the piston, the piston including hollow spaces through which a coolant flows to cool the piston, a first oil circulating system for lubricating the shaft and piston bearings, the first system including first passages for conducting lubricating oil to the bearings, a first pump for pumping lubricating oil from a source through the first passages to the bearings, said first pump having a capacity to deliver oil in small volume and at a high pressure, a second independent oil circulating system for directing an oil coolant to the piston, the second system including second passages for conducting the coolant to the piston hollow spaces to cool the piston, a second pump for pumping the coolant from a source through the second passages to the piston hollow spaces, said second pump having a capacity to deliver the coolant in large volume and at low pressure, a return passage for receiving and directing the coolant from the piston hollow spaces, a valve in one of the second passages and being adapted to be shifted to an adjusted position to regulate the amount of coolant passing through the second passages, a condition responsive control means coupled with the valve for shifting the valve to an adjusted position for adjusting the amount of coolant passing through the second passages into the piston hollow spaces to thereby permit throttling the amount of coolant passing into the piston hollow spaces, and the condition responsive means being coupled with the return passage for sensing temperature of the coolant in the return passage for adjusting the valve.

* =l =l l 

1. A rotary piston combustion engine comprising: a housing, a shaft mounted in the housing, shaft bearings interposed between the shaft and the housing, an eccentric on the shaft, a rotary piston carried by the eccentric, a piston bearing interposed between the eccentric and the piston, the piston including hollow spaces through which a coolant flows to cool the piston, a first oil circulating system for lubricating the shaft and piston bearings, the first system including first passages for conducting lubricating oil to the bearings, a first pump for pumping lubricating oil from a source through the first passages to the bearings, said first pump having a capacity to deliver oil in small volume and at a high pressure, a second independent oil circulating system for directing an oil coolant to the piston, the second system including second passages for conducting the coolant to the piston hollow spaces to cool the piston, a second pump for pumping the coolant from a source through the second passages to the piston hollow spaces, said second pump having a capacity to deliver the coolant in large volume and at low pressure, a return passage for receiving and directing the coolant from the piston hollow spaces, a valve in one of the second passages and being adapted to be shifted to an adjusted position to regulate the amount of coolant passing through the second passages, a condition responsive control means coupled with the valve for shifting the valve to an adjusted position for adjusting the amount of coolant passing through the second passages into the piston hollow spaces to thereby permit throttling the amount of coolant passing into the piston hollow spaces, and the condition responsive means being coupled with the return passage for sensing temperature of the coolant in the return passage for adjusting the valve. 